A variety of devices and procedures for generating electrical energy from radioactive energy have been previously attempted by others with varying degrees of failure. However, the devices and procedures have been essentially directed to the utilization of only a single type of particle (i.e. the alpha, beta, or gamma particle) emitted from a particular nuclear energy source, and have understandably yielded very inefficient and impractical amounts of electrical energy.
For example, U.S. Pat. No. 4,178,524, which issued to J. Ritter on Dec. 11, 1979, describes a radioisotope photoelectric generator which relies solely upon photoelectric generation from gamma radiation emitted by a radioactive source. In particular, the Ritter device relies on photoelectric generation as a result of incident gamma radiation impacting a thin, high atomic number, or "high-Z", material which releases electrons as a result of the impact for capture by a thicker low atomic number, or "low-Z", material. Electrons captured by the low-Z material produce a potential difference build-up between adjacent sheets, and such potential is used to provide electric current. The inefficiency of the Ritter system, however, is specifically set forth in the specification where it is emphasized that one high-Z/low-Z pair of sheets will absorb only about 5% of the incident photons emitted by the radioisotope source. Moreover, devices such as described in Ritter require a custom tailored fuel source (e.g. one which emits gamma photons, but no high-energy charged particles), which can cause undue expense and difficulty in obtaining fuel.
Similarly, the devices set forth in U.S. Pat. Nos. 2,527,945 and 2,552,050, which issued to E. Linder on Oct. 31, 1950 and May 8, 1951, respectively, call for a single emitter source of fuel (i.e. either an alpha or beta particle emitter); U.S. Pat. No. 2,858,459, which issued to E. Schwarz on Oct. 28, 1958 calls specifically for a primary beta emitter; and U.S. Pat. No. 3,290,522, which issued to R. Ginell on Dec. 6, 1966 calls for a radioactive source of beta particles. Because these devices rely solely upon a single particle for generation of electrical energy, they are inherently inefficient and impractical in use. Specifically, requiring a primary emitter of only a single particular particle ignores the fact that radioactive decay necessarily transmutes elements through a chain or family of elements which may themselves emit particles other than the primary particle required in any particular device. It is virtually impossible to isolate a pure alpha or beta particle emitter unless it is the last element in a family chain just prior to stability. Failure to recognize this fact necessarily means that these devices generally fail to take advantage of two of the three particles commonly emitted during radioactive decay.
Specifically, the devices set forth in the Linder '050 and '945 patents require shielding the radioactive source to ensure that only alpha particles or beta particles (but not both) are permitted to impact the collector electrode of the device. As it is understood that radioactive material will emit both alpha and beta particles, Linder attempts to minimize the natural neutralization of the charge build-up on the collector electrode if both particles were permitted to impact the electrode. Consequently, the shielded particles are essentially wasted in the process.
The Schwarz '459 disclosure describes situating a primary beta emitter source within a highly evacuated spherical radiation collector. While the Schwarz device utilizes a secondary emitter provided between the primary beta emitter and the collector to attempt to increase the efficiency of the device, the device by its nature is only equipped to utilize one particular particle, and requires a highly specialized fuel source.
The electrical generator set forth in the Ginell '522 reference contemplates the generation of electrical power by modulating the density of a cloud of charged beta particles confined within a glass sphere having an inner surface coated with silver. The hollow sphere and its silver lining are connected to a gas discharge tube, and the beta particles or electrons emitted by the radioactive source are collected by the silver lining and accumulate thereon to create an electrostatic charge between the silver lining and the hollow sphere. When this electrostatic charge reaches a given value, the discharge tube fires, equalizing the potentials of the sphere and the lining and allowing the cloud of charged particles to expand within the sphere. As the electrostatic charge begins to build again, the cloud of charged particles is compressed until the discharge tube again fires. The variation in density of the cloud of charged particles cuts an electrically conductive means to create an electric potential and current in accordance with Faraday's Law of Induction. Consequently, the Ginell device operates in a manner similar to a transformer and relies on a single emitted particle. The specification of Ginell further specifically recognizes a 50% loss of efficiency due to self-absorption and capture of charged particles by the spherical shell.
More recently, in acknowledgment of the fact that there has been a rapid increase over the years in the amount of radioactive substances available in the wake of atomic energy power generation, research has been carried out to try to find uses for these radioactive substances and for the conversion of radioactive energy into electric energy. U.S. Pat. No. 3,939,366, which issued to Y. Ato et al. on Feb. 17, 1976 discloses a two-step converting-type system wherein radioactive energy is used to induce a physical phenomenon which is, in turn, used to produce electric. The Ato device requires processed fuel for providing either an alpha particle source or a low energy beta particle source. This radioactive source of primarily a single type of particles is used to release electrons within a converter body, and a magnetic field is used to guide those released electrons to a particular electrode for collection. In addition to requiring a particular primary emitter source of processed fuel, this device is additionally inefficient as it makes use of only a single axial plane of emission of particles, thereby wasting a high percentage of that single type of particle.
U.S. Pat. No. 4,835,433, which issued to P. Brown on May 30, 1989, discloses a rather complex assembly of elements to form an equivalent resonant circuit utilizing an array of capacitors, inductors and transformer windings to convert radioactive energy in the form of alpha particles or beta particles into electrical energy. In particular, Brown contemplates utilization of a radium needle surrounded by a cylinder of thorium having a plurality of uranium rods positioned therewithin, all surrounded by a series of transformers and with the entire unit being placed in an oil filled can with heat sinks. The Brown device assumes that there is no direct current resistance and fails to take advantage of particles emitted by the radioactive source in planes which do not intersect with the electrical circuitry of the device. Similarly, Brown is inherently inefficient in relying on only a single type of emitted particle from the radioactive source, and by creating electrical energy only indirectly through a transformer closed circuit configuration. Additionally, the Brown apparatus calls specifically for heat sinks to absorb thermal energy produced by the system, thereby wasting an additional source of electrical current.
Additionally, many of the devices heretofore available for converting the products of radioactive decay into electrical energy have failed to take into account the fact that when alpha particles strike any atom with an atomic number greater than 19, the result is ionization and the creation of helium atoms which are generally incapable of chemically combining with other materials within these devices. Consequently, the build up of helium gas within these systems is generally unavoidable, and could eventually impede the operation and/or cause unsafe pressure buildups therewithin. Moreover, the devices previously available have relied upon the theoretical use of pure radioactive material which emit only a single type of particle. In fact, radioactive decay generally provides for the emission of alpha, beta and gamma photons or particles (the terms "gamma particles" and "gamma photons" will be used interchangeably herein) which, by their very nature, tend to neutralize each other reducing by up to 50% the useable power (i.e. the potential difference within the system) and the overall efficiency thereof.
As a result, heretofore there has not been available in the industry an efficient device for converting atomic energy into electrical current, nor devices which are capable of taking advantage of more than one of the various particles commonly released during radioactive decay in order to produce more energy from the same amount of source material. Similarly, while it has clearly been recognized in the industry that simple, reliable and efficient atomic "batteries" are desirable, none of the apparatuses or methods previously available have adequately responded to this need.